A light emitting diode (LED) is a semiconductor device constituted mainly by group III-V compound semiconductor materials. Since such semiconductor materials have a characteristic of converting electricity into light, when a current is applied to the semiconductor materials, electrons and holes therein would be combined and release excessive energy in a form of light, thereby achieving an effect of luminosity.
A vertical LED apparatus is a common LED apparatus. In a vertical LED apparatus, an LED chip consists of a silicon substrate and a light emitting layer disposed on the silicon substrate. The silicon substrate is disposed on a carrier board, and the LED chip is electrically connected to the carrier board through a bonding wire. Compared to a conventional face-up LED apparatus, the vertical LED apparatus has advantages such as good heat dissipation and lower occurrence of current crowding.
Nonetheless, due to a difference in expansion coefficient between the bonding wire and a sealant in the vertical LED apparatus, breakage easily occurs to result in a failure of the apparatus. In addition, uneven distribution of phosphor in the sealant occurs as a consequence of natural deposition of the phosphor itself and excessively large thickness of the bonding wire and the LED chip. Moreover, since the LED chip is electrically connected to the carrier board through the bonding wire, density of the LED chips in the vertical LED apparatus cannot be further decreased. For a projection type light source that requires multiple chips, luminous intensity per unit area cannot be effectively enhanced.